- The earliest period of the Paleozoic era, spanning the time between 544 and 505 million years ago. It is named after Cambria, the Roman name for Wales, where rocks of this age were first studied.
- earliest geologic period in which fossils are found abundantly
Source: Noland, George B. 1983. General Biology, 11th Edition. St. Louis, MO. C. V. Mosby